Synthesis and characterization of poly(amideimide)s from 4-(p-carboxyphenoxy)phthalic anhydride and 4-(p-carboxybenzoyl) phthalic anhydride S. Rajasekar, D. Venkatesan * Department of Chemistry, School of Chemical and Biotechnology, Sastra University, Thanjavur 613 401, Tamilnadu, India article info Article history: Received 30 May 2013 Received in revised form 7 August 2013 Accepted 16 August 2013 Available online 24 August 2013 Keywords: Poly(amideimide)s High performance polymers Thermal properties abstract A series of poly(amideimide)s were prepared by the reaction of two new anhydride acidchloride monomers with aromatic diamines. 4-(p-Carboxyphenoxy)phthalic anhydride was synthesized by nucleophilic displacement reaction of N-methyl-4-nitrophthalimide with p-hydroxybenzoic acid, fol- lowed by hydrolysis. The tricarboxylic acid was converted to the corresponding anhydride acidchloride. 4-(p-Carboxybenzoyl)phthalic anhydride was synthesized by FriedeleCraft’s acylation of toluene with N- phenylphthalimide-4-carbonylchloride, which was then converted to anhydride acidchloride of 4-(p- carboxybenzoyl)phthalic acid. The monomers were characterized by IR and NMR. Several PAI were prepared by the reaction of these anhydride acidchloride monomers with aromatic diamines. The inherent viscosities of the polymers were in the range of 0.42e0.58 dL/g. All polymers were soluble in polar aprotic solvents. The polymers showed good thermal stability and T g values were in the range of 226e269  C. X-Ray diffractograms of polymers indicate amorphous nature of these polymers. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Aromatic polyimides are important class of high performance polymeric materials that has outstanding thermal stability, excellent mechanical properties and good chemical resistance [1e 4]. These polymers are widely used in aerospace, electronics and automobile industries [5,6]. However, aromatic polyimides have close packed polymer chains due to the strong intermolecular forces and these polymers have very high melting points and limited solubility in organic solvents [7e11]. In order to improve the processability of aromatic polyimides, polymers have been prepared from structurally modified dianhydrides and diamines [12]. The other structural modifications include incorporation of flexible groups such as aryl ether, thioether and carbonyl linkages into the polymer backbone [13,14], incorporation of groups such as amide, ester, etc. to obtain polyimide derivatives such as pol- y(amideimide)s, poly(esterimide)s, etc. and introducing sub- stituents in the aromatic groups present in the polymer backbone [15e19]. Among modified polyimides, poly(amideimide)s are the most successful materials (e.g. Torlons Ò ). The poly(amideimide)s are generally prepared by the polycondensation of trimellitic anhy- dride chloride or aromatic diacids containing preformed imide rings with aromatic diamines [20e23]. In the present work, two new monomers 4-(p-carboxyphenoxy) phthalic anhydride and 4-(p-carboxybenzoyl)phthalic anhydride were synthesized and polymers were prepared by the poly- condensation of these anhydride acidchloride monomers with several aromatic diamines. These polymers showed good thermal stability comparable to aromatic polyimides. The improved pro- cessability of these polymers compared to polyimides results from the incorporation of amide groups into polymer backbone. 2. Materials and methods 2.1. Materials N-Methyl-4-nitrophthalimide, 4-hydroxy benzoic acid and tri- mellitic anhydride were used as received. Aniline, toluene, thionyl chloride and pyridine were purified by distillation. The commer- cially available aromatic diamines such as m-phenylenediamine, oxydianiline, methylenedianiline and 4,4 0 -diaminodiphenyl sul- fone were purified by recrystallization. Dimethylsulfoxide (DMSO), * Corresponding author. E-mail addresses: dvenkatesan@chem.sastra.edu, dvenkat66@yahoo.co.in (D. Venkatesan). Contents lists available at ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer 0032-3861/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.polymer.2013.08.037 Polymer 54 (2013) 5626e5633